1. Field of the Invention
This invention relates to a method for manufacturing a magneto-resistance effect element and a magnetic recording and reproducing apparatus.
2. Background Art
Performance of a magnetic device, particularly such as a magnetic head is extremely enhanced by using Giant Magneto-Resistive Effect (GMR). Particularly, since a spin valve film (SV film) can exhibit a larger GMR effect, the SV film has developed the magnetic device such as a magnetic head and MRAM (Magnetic Random Access Memory).
The “spin valve” film is laminated films having such a structure as sandwiching a non-magnetic metal spacer layer between two ferromagnetic layers and is called as spin depending scattering unit. In the spin valve film, the magnetization of one ferromagnetic layer (often called as a “pinning layer” or “fixed magnetization layer”) is fixed by the magnetization of an anti-ferromagnetic layer and the magnetization of the other ferromagnetic layer (often called as a “free layer” or “free magnetization layer”) can be rotated in accordance with an external magnetic field. In the spin valve film, an electric resistance changes by varying a relative angle between the magnetizations of the pinning layer and the free layer. The value of the change in the electric resistance is called as MR (Magneto Resistance) variation ratio, and corresponds to an output of the element.
As a magneto-resistance effect element using the spin valve film, a CIP (Current In plane)-GMR element, a TMR (Tunneling Magneto Resistance) element and a CPP (Current Perpendicular to Plane)-GMR element are proposed. Among these elements, the CIP element was put to first practical use. In the CIP-GMR element, a sense current is flowed to the SV film in the direction parallel to the film surface thereof and it was in practice use during a period with a large head size. However, when a head size becomes small with increasing of the recording density in a HDD, a heat or the like become problem and the TMR element, in which a sense current is flowed to the film in the direction perpendicular to the film surface thereof was put to practical use next. In the TMR element has a merit of a small sense current and large output. However, the resistance in the TMR element is usually high because it uses a tunneling current through an insulating barrier. It will become problem not to decrease the resistance of the element in future when the recording density is increased and the head size is downsized.
To solve this problem, the CPP-GMR element has been proposed. The resistance of the element in the CPP-GMR element is low by nature, because it uses a magneto-resistance effect by a metal conduction. This is the merit of the CPP-GMR element comparing with the TMR element.
In a metallic CPP-GMR element in which the SV film is made of metallic films, the variation degree in resistance by the magnetization of the SV film becomes small so that to convert a weak magnetic field (for example, from a magnetic disk of high recording density) to an electric signal becomes difficult.
In contrast, such a CPP element using an oxide layer with a conductive portion along with the direction of film thickness (NOL: Nano-oxide layer) is proposed in JP-A 2002-208744 (KOKAI) (Patent document 1). In the CPP element, the element resistance and the MR variation degree of the element can be developed by means of CCP (Current-confined-path) effect. Hereinafter, this element is often called as a “CCP-CPP element”.
However, it is anticipated that from now, applications of magnetic recording devices will be further enlarged and higher-density recording will be achieved, and in this case, it becomes necessary to provide a magneto-resistance effect element having further higher output.
In the case of CCP-CPP element, because current is confined in a spacer, contribution of electric conduction in the conductive portion to GMR effect is very large. Specifically, it has been reported that a MR variation ratio becomes higher as decreasing the electric resistance of the conductive portion in IEEE Trans. Magn. 40 p. 2236, (2004) (Non-patent document 1).
As a means for realizing the CCP-CPP element, a method for manufacturing a spacer has been proposed in JP-A 2006-54257 (Kokai) (Patent document 2).
However, for achieving the MR variation ratio anticipated to be required in the future, further ingenuity is required. That is, it is desired to develop technologies to improve the conductivity of the conductive portion further and improve the MR variation ratio while maintaining the insulating characteristics of the insulating layer.
As a means for decreasing the electric resistance of the conductive portion, there is a method to decreasing further an amount of impurities included in non-magnetic metal forming the conductive portion. Among impurities, by decreasing oxygen impurities, the electric resistance can be decreased. For decreasing the amount of the oxygen impurities, it is effective to reduce the conductive portion. For a reduction effect by a gas in the vacuum chamber, for example, in copper wiring used in a semiconductor device or the like, a technique of removing copper oxide by treatment with hydrogen plasma is known in U.S. Pat. No. 6,033,584 (Patent document 3).